As a background art in this technical field, there is disclosed in JP-A-2011-102714 (PTL 1). PTL 1 describes that “a noise detection process during a cycle for a MS spectrum collection is provided so that an ion detection signal is compared with the detected noise so as to remove the noise and to remove the neutral particle noise corresponding to the fluctuation of a sample and a carrier gas which are changed during the measurement”. In addition, it is described that “a noise component can be removed by performing a comparison operation between the signal and the noise which are detected during a spectrum acquisition period and a noise acquisition period.